This invention relates generally to radio frequency antennas and more particularly to feed networks for use in multi-element monopulse antenna systems.
As is known in the art, a monopulse antenna, in its most basic configuration, includes a cluster of four horns, or antenna elements, disposed in four quadrants of an array, such elements being coupled to a monopulse arithmetic unit to provide sum, azimuth and elevation antenna patterns. In many applications, however, additional antenna elements are required in order to improve the sidelobe characteristics of either relatively small array monopulse antennas or monopulse antennas using a multielement feed for a radio frequency lens or reflector. One such multi-element monopulse antenna is discussed in an article entitled "A Multi-element High Power Monopulse Feed With Low Sidelobes and High Aperture Efficiency," by H. S. Wong, R. Tang and E. E. Barber, published in IEEE Transactions on Antenna and Propagation, Vol. AP-22, No. 3, May 1974. In such multi-element monopulse antenna independent control of the sum, azimuth and elevation antenna patterns is provided by grouping the antenna elements in sets of four, forming sum and difference outputs for each set using four hybrids and combining such outputs with power dividers to form a sum output azimuth output and elevation output.